23 results on '"Attila Bényei"'
Search Results
2. 'Inverted' Cyclic(Alkyl)(Amino)Carbene (CAAC) Ruthenium Complex Catalyzed Isomerization Metathesis (ISOMET) of Long Chain Olefins to Propylene at Low Ethylene Pressure
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Vajk Farkas, Dániel Csókás, Ádám Erdélyi, Gábor Turczel, Attila Bényei, Tibor Nagy, Sándor Kéki, Imre Pápai, and Róbert Tuba
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inverted CAAC ,ISOMET ,metathesis ,propylene ,ruthenium ,Science - Abstract
Abstract Isomerization Metathesis (ISOMET) reaction is an emerging tool for “open loop” chemical recycling of polyethylene to propylene. Novel, latent N‐Alkyl substituted Cyclic(Alkyl)(Amino)Carbene (CAAC)–ruthenium catalysts (5a‐Ru, 3b‐Ru – 6c‐Ru) are developed rendering “inverted” chemical structure while showing enhanced ISOMET activity in combination with (RuHCl)(CO)(PPh3)3 (RuH) double bond isomerization co‐catalyst. Systematic investigations reveal that the steric hindrance of the substituents on nitrogen and carbon atom adjacent to carbene moiety in the CAAC ligand have significantly improved the catalytic activity and robustness. In contrast to the NHC‐Ru and CAAC‐Ru catalyst systems known so far, these systems show higher isomerization metathesis (ISOMET) activity (TON: 7400) on the model compound 1‐octadecene at as low as 3.0 bar optimized pressure, using technical grade (3.0) ethylene. The propylene content formed in the gas phase can reach up to 20% by volume. more...
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- 2024
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Catalog
3. Half-Sandwich Type Platinum-Group Metal Complexes of C-Glucosaminyl Azines: Synthesis and Antineoplastic and Antimicrobial Activities
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István Kacsir, Adrienn Sipos, Evelin Major, Nikolett Bajusz, Attila Bényei, Péter Buglyó, László Somsák, Gábor Kardos, Péter Bai, and Éva Bokor
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ruthenium ,osmium ,iridium ,rhodium ,half-sandwich complex ,C-glucosaminyl heterocycles ,Organic chemistry ,QD241-441 - Abstract
While platinum-based compounds such as cisplatin form the backbone of chemotherapy, the use of these compounds is limited by resistance and toxicity, driving the development of novel complexes with cytostatic properties. In this study, we synthesized a set of half-sandwich complexes of platinum-group metal ions (Ru(II), Os(II), Ir(III) and Rh(III)) with an N,N-bidentate ligand comprising a C-glucosaminyl group and a heterocycle, such as pyridine, pyridazine, pyrimidine, pyrazine or quinoline. The sugar-containing ligands themselves are unknown compounds and were obtained by nucleophilic additions of lithiated heterocycles to O-perbenzylated 2-nitro-glucal. Reduction of the adducts and, where necessary, subsequent protecting group manipulations furnished the above C-glucosaminyl heterocycles in their O-perbenzylated, O-perbenzoylated and O-unprotected forms. The derived complexes were tested on A2780 ovarian cancer cells. Pyridine, pyrazine and pyridazine-containing complexes proved to be cytostatic and cytotoxic on A2780 cells, while pyrimidine and quinoline derivatives were inactive. The best complexes contained pyridine as the heterocycle. The metal ion with polyhapto arene/arenyl moiety also impacted on the biological activity of the complexes. Ruthenium complexes with p-cymene and iridium complexes with Cp* had the best performance in ovarian cancer cells, followed by osmium complexes with p-cymene and rhodium complexes with Cp*. Finally, the chemical nature of the protective groups on the hydroxyl groups of the carbohydrate moiety were also key determinants of bioactivity; in particular, O-benzyl groups were superior to O-benzoyl groups. The IC50 values of the complexes were in the low micromolar range, and, importantly, the complexes were less active against primary, untransformed human dermal fibroblasts; however, the anticipated therapeutic window is narrow. The bioactive complexes exerted cytostasis on a set of carcinomas such as cell models of glioblastoma, as well as breast and pancreatic cancers. Furthermore, the same complexes exhibited bacteriostatic properties against multiresistant Gram-positive Staphylococcus aureus and Enterococcus clinical isolates in the low micromolar range. more...
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- 2023
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4. Synthesis of Multifunctional Aryl(trifloxyalkenyl)iodonium Triflate Salts
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Balázs L. Tóth, Ferenc Béke, Orsolya Egyed, Attila Bényei, András Stirling, and Zoltán Novák
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Chemistry ,QD1-999 - Published
- 2019
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5. Investigation of the Drug Carrier Properties of Insoluble Cyclodextrin Polymer Microspheres
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Ádám Haimhoffer, Alexandra Vas, Gabriella Árvai, Éva Fenyvesi, László Jicsinszky, István Budai, Attila Bényei, Géza Regdon, Ágnes Rusznyák, Gábor Vasvári, Judit Váradi, Ildikó Bácskay, Miklós Vecsernyés, and Ferenc Fenyvesi more...
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insoluble cyclodextrin polymer ,cyclodextrin beads ,curcumin ,estradiol-glow ,complexation ,drug delivery ,Microbiology ,QR1-502 - Abstract
The investigation of the usability of solid insoluble β-cyclodextrin polymers (βCDP) in micro-sized, controlled drug delivery systems has only recently attracted interest. Our aim was to form complexes with poorly soluble active pharmaceutical ingredients (APIs) with two types of βCDP for drug delivery applications. Solid insoluble cyclodextrin polymer of irregular shape (βCDPIS) and cyclodextrin microbeads (βCDPB) were used in the experiments. Morphology, surface area, size distribution and swelling capacity of carriers were investigated. We created complexes with two APIs, curcumin and estradiol, and applied powder X-ray diffraction, FTIR and thermal analysis (TGA/DSC) to prove the complexation. Finally, the dissolution, biocompatibility and permeation of APIs on Caco-2 cells were investigated. The size of the beads was larger than 100 µm, their shape was spherical and surfaces were smooth; while the βCDPIS particles were around 4 µm with irregular shape and surface. None of the polymers showed any cytotoxic effect on Caco-2 cells. Both carriers were able to extract curcumin and estradiol from aqueous solutions, and the dissolution test showed prolonged estradiol release. Caco-2 permeability tests were in accordance with the complexation abilities and dissolution of the complexes. This study offers useful data for further pharmaceutical applications of insoluble cyclodextrin polymers. more...
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- 2022
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6. Highly Selective Synthesis of 6-Glyoxylamidoquinoline Derivatives via Palladium-Catalyzed Aminocarbonylation
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Sami Chniti, László Kollár, Attila Bényei, and Attila Takács
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double carbonylation ,palladium ,aminocarbonylation ,6-iodoquinoline ,carbon monoxide ,Organic chemistry ,QD241-441 - Abstract
The aminocarbonylation of 6-iodoquinoline has been investigated in the presence of large series of amine nucleophiles, providing an efficient synthetic route for producing various quinoline-6-carboxamide and quinoline-6-glyoxylamide derivatives. It was shown, after detailed optimization study, that the formation of amides and ketoamides is strongly influenced by the reaction conditions. Performing the reactions at 40 bar of carbon monoxide pressure in the presence of Pd(OAc)2/2 PPh3, the corresponding 2-ketocarboxamides were formed as major products (up to 63%). When the monodentate triphenylphosphine was replaced by the bidentate XantPhos, the quinoline-6-carboxamide derivatives were synthesized almost exclusively under atmospheric conditions (up to 98%). The isolation and characterization of the new carbonylated products of various structures were also accomplished. Furthermore, the structure of three new mono- and double-carbonylated compounds were unambiguously established by using a single-crystal XRD study. more...
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- 2021
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7. Syntheses and Study of a Pyrroline Nitroxide Condensed Phospholene Oxide and a Pyrroline Nitroxide Attached Diphenylphosphine
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Mostafa Isbera, Balázs Bognár, Ferenc Gallyas, Attila Bényei, József Jekő, and Tamás Kálai
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lithiation ,McCormac reaction ,nitroxides ,protecting groups ,reduction ,Organic chemistry ,QD241-441 - Abstract
The reaction of a diene nitroxide precursor with dichlorophenylphosphine in a McCormac procedure afforded 1,1,3,3-tetramethyl-5-phenyl-1,2,3,4,5,6-hexahydrophospholo[3,4-c]pyrrole-5-oxide-2-oxyl. Lithiation of the protected 3-iodo-pyrroline nitroxide followed by treatment with chlorodiphenylphosphine after deprotection afforded (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-3-yl)diphenylphosphine oxide, and after reduction, (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-3-yl)diphenylphosphine was realized, which was also supported by X-ray single crystal diffraction measurements. This pyrroline diphenylphosphine derivative was converted to hexadecylphosphonium salt, which is an analogue of antineoplastic agent, MITO-CP. more...
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- 2021
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8. Synthesis and HPLC-ECD Study of Cytostatic Condensed O,N-Heterocycles Obtained from 3-Aminoflavanones
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Ádám Szappanos, Attila Mándi, Katalin Gulácsi, Erika Lisztes, Balázs István Tóth, Tamás Bíró, Anita Kónya-Ábrahám, Attila Kiss-Szikszai, Attila Bényei, Sándor Antus, and Tibor Kurtán
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neber rearrangement ,3-aminoflavanones ,antiproliferative activity ,TDDFT-ECD calculations ,HPLC-ECD ,3-(N-chloroacetylamino)-flavan-4-ol ,Microbiology ,QR1-502 - Abstract
Racemic chiral O,N-heterocycles containing 2-arylchroman or 2-aryl-2H-chromene subunit condensed with morpholine, thiazole, or pyrrole moieties at the C-3-C-4 bond were synthesized with various substitution patterns of the aryl group by the cyclization of cis- or trans-3-aminoflavanone analogues. The 3-aminoflavanone precursors were obtained in a Neber rearrangement of oxime tosylates of flavanones, which provided the trans diastereomer as the major product and enabled the isolation of both the cis- and trans-diastereomers. The cis- and trans-aminoflavanones were utilized to prepare three diastereomers of 5-aryl-chromeno[4,3-b][1,4]oxazines. Antiproliferative activity of the condensed heterocycles and precursors was evaluated against A2780 and WM35 cancer cell lines. For a 3-(N-chloroacetylamino)-flavan-4-ol derivative, showing structural analogy with acyclic acid ceramidase inhibitors, 0.15 μM, 3.50 μM, and 6.06 μM IC50 values were measured against A2780, WM35, and HaCat cell lines, and apoptotic mechanism was confirmed. Low micromolar IC50 values down to 2.14 μM were identified for the thiazole- and pyrrole-condensed 2H-chromene derivatives. Enantiomers of the condensed heterocycles were separated by HPLC using chiral stationary phase, HPLC-ECD spectra were recorded and TDDFT-ECD calculations were performed to determine the absolute configuration and solution conformation. Characteristic ECD transitions of the separated enantiomers were correlated with the absolute configuration and effect of substitution pattern on the HPLC elution order was determined. more...
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- 2020
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9. Effect of Molecular Weight on the Dissolution Profiles of PEG Solid Dispersions Containing Ketoprofen
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Ha Pham Le Khanh, Ádám Haimhoffer, Dániel Nemes, Liza Józsa, Gábor Vasvári, István Budai, Attila Bényei, Zoltán Ujhelyi, Pálma Fehér, and Ildikó Bácskay
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Polymers and Plastics ,General Chemistry ,solid dispersion ,polyethylene glycol ,PEG ,ketoprofen ,solubility ,dissolution - Abstract
Solid dispersions are typically binary systems with a hydrophilic matrix polymer and a lipophilic active substance. During formulation, the drug undergoes a crystalline to amorphous phase transition, which leads to a supersaturated solution providing enhanced bioavailability. The interaction of the active substance and the polymer is unique and influences the level of supersaturation. We aimed to investigate the relationship between low molecular weight polyethylene glycol derivates PEG 1000, 1500, and 2000 and ketoprofen regarding the effect of molecular weight. The physicochemical properties of solid dispersions prepared with hot melt homogenization and their respective physical mixtures were investigated with Fourier transform infrared spectroscopy, powder X-ray diffraction and scanning electron microscopy techniques. A phase solubility study was carried out in hydrochloric acid media which showed no difference between the three polymers, but the dissolution curves differed considerably. PEG 1000 had higher percentage of released drug than PEG 1500 and 2000, which had similar results. These results indicate that when multiple low molecular weight PEGs are suitable as matrix polymers of solid dispersions, the molecular weight has only limited impact on physicochemical characteristics and interactions and further investigation is needed to select the most applicable candidate. more...
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- 2023
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10. The ortho effect in directed C–H activation†
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Attila Domján, Zoltán Novák, Orsolya Egyed, Balázs L. Tóth, Anna Monory, Bálint Szathury, András Stirling, and Attila Bényei
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Steric effects ,Reaction conditions ,Reaction rate ,Work (thermodynamics) ,Chemistry ,Computational chemistry ,Metalation ,Substrate (chemistry) ,Reactivity (chemistry) ,General Chemistry ,Dihedral angle - Abstract
The success of transition metal-catalysed ortho-directed C–H activation is often plagued by the effects of undesirable interactions between the directing group (DG) and other groups introduced into the aromatic core of the substrate. In particular, when these groups are in neighbouring positions, their interactions can affect profoundly the efficacy of the C–H activation by transition metals. In this work we introduce a simple substrate-only-based model to interpret the influence of steric hindrance of a group in ortho position to the DG in directed ortho-C–H bond activation reactions, and coined the term Ortho Effect (OE) for such situations. We consider simple descriptors such as torsion angle and torsional energy to predict and explain the reactivity of a given substrate in directed C–H activation reactions. More than 250 examples have been invoked for the model, and the nature of the ortho effect was demonstrated on a wide variety of structures. In order to guide organic chemists, we set structural and energetic criteria to evaluate a priori the efficiency of the metalation step which is usually the rate-determining event in C–H activations, i.e. we provide a simple and general protocol to estimate the reactivity of a potential substrate in C–H activation. For borderline cases these criteria help set the minimum reaction temperature to obtain reasonable reaction rates. As an example for the practical applicability of the model, we performed synthetic validations via palladium-catalysed 2,2,2-trifluoroethylation reactions in our lab. Furthermore, we give predictions for the necessary reaction conditions for several selected DGs., The term and concept of Ortho Effect (OE) is introduced for the description of steric effects in transition metal catalyzed directed ortho C–H activation reactions to explain and predict reactivities of substrates. more...
- Published
- 2021
11. Reactive Oxygen Species Production Is Responsible for Antineoplastic Activity of Osmium, Ruthenium, Iridium and Rhodium Half-Sandwich Type Complexes with Bidentate Glycosyl Heterocyclic Ligands in Various Cancer Cell Models
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Bokor, István Kacsir, Adrienn Sipos, Attila Bényei, Eszter Janka, Péter Buglyó, László Somsák, Péter Bai, and Éva
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osmium complex ,iridium complex ,ruthenium complex ,rhodium complex ,half-sandwich ,cooperative binding ,reactive oxygen species production ,glycosyl heterocycle ,oxadiazole ,triazole ,ovarian cancer ,Hodgkin’s lymphoma ,osteosarcoma - Abstract
Platinum complexes are used in chemotherapy, primarily as antineoplastic agents. In this study, we assessed the cytotoxic and cytostatic properties of a set of osmium(II), ruthenium(II), iridium(III) and rhodium(III) half-sandwich-type complexes with bidentate monosaccharide ligands. We identified 5 compounds with moderate to negligible acute cytotoxicity but with potent long-term cytostatic activity. These structure-activity relationship studies revealed that: (1) osmium(II) p-cymene complexes were active in all models, while rhodium(III) and iridium(III) Cp* complexes proved largely inactive; (2) the biological effect was influenced by the nature of the central azole ring of the ligands—1,2,3-triazole was the most effective, followed by 1,3,4-oxadiazole, while the isomeric 1,2,4-oxadiazole abolished the cytostatic activity; (3) we found a correlation between the hydrophobic character of the complexes and their cytostatic activity: compounds with O-benzoyl protective groups on the carbohydrate moiety were active, compared to O-deprotected ones. The best compound, an osmium(II) complex, had an IC50 value of 0.70 µM. Furthermore, the steepness of the inhibitory curve of the active complexes suggested cooperative binding; cooperative molecules were better inhibitors than non-cooperative ones. The cytostatic activity of the active complexes was abolished by a lipid-soluble antioxidant, vitamin E, suggesting that oxidative stress plays a major role in the biological activity of the complexes. The complexes were active on ovarian cancer, pancreatic adenocarcinoma, osteosarcoma and Hodgkin’s lymphoma cells, but were inactive on primary, non-transformed human fibroblasts, indicating their applicability as potential anticancer agents. more...
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- 2022
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12. The first synthesis of 3-deoxyoripavine and its utilization in the preparation of 10-deoxyaporphines and cyprodime
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Attila Sipos, Attila Bényei, Antal Udvardy, and Sándor Berényi
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Cyprodime ,Chemistry ,medicine.drug_class ,Stereochemistry ,Biological activity ,reduction ,General Chemistry ,Serotonergic ,cyprodime ,Materials Chemistry ,medicine ,oripavine ,10-deoxyaporphines ,acid-catalyzed rearrangement ,QD1-999 ,Opioid antagonist - Abstract
The synthesis of 3-deoxyoripavine (7) was realized as a novel and promising intermediate towards the synthesis of the important class of dopaminergic and/or serotonergic 10-deoxyaporphines and the special pharmacological tool µ opioid antagonist cyprodime. Generally, the preparation of these valuable biologically active compounds was achieved in remarkable yields. more...
- Published
- 2013
13. Complexation of Ln 3+ Ions with Cyclam Dipicolinates: A Small Bridge that Makes Huge Differences in Structure, Equilibrium, and Kinetic Properties
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David Esteban-Gómez, Teresa Rodríguez-Blas, Aurora Rodríguez-Rodríguez, Andrés de Blas, Ferenc K. Kálmán, Gyula Tircsó, Imre Tóth, Attila Bényei, Carlos Platas-Iglesias, Raphaël Tripier, Martín Regueiro-Figueroa, Departamento de Química Fundamental, Universidade da Coruña, Chimie, Electrochimie Moléculaires et Chimie Analytique (CEMCA), Institut Brestois Santé Agro Matière (IBSAM), Université de Brest (UBO)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Faculty of Science and Technology, University of Debrecen, Department of Pharmaceutical Chemistry, and University of Debrecen Egyetem [Debrecen] more...
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Lanthanide ,Aqueous solution ,010405 organic chemistry ,Chemistry ,Ligand ,Metal ions in aqueous solution ,Inorganic chemistry ,010402 general chemistry ,01 natural sciences ,Dissociation (chemistry) ,0104 chemical sciences ,Inorganic Chemistry ,Metal ,Crystallography ,chemistry.chemical_compound ,Természettudományok ,visual_art ,Cyclam ,visual_art.visual_art_medium ,Molecule ,[CHIM]Chemical Sciences ,Physical and Theoretical Chemistry ,Kémiai tudományok - Abstract
The coordination properties toward the lanthanide ions of two macrocyclic ligands based on a cyclam platform containing picolinate pendant arms have been investigated. The synthesis of the ligands was achieved by using the well-known bis-aminal chemistry. One of the cyclam derivatives (cb-tedpa(2-)) is reinforced with a cross-bridge unit, which results in exceptionally inert [Ln(cb-tedpa)](+) complexes. The X-ray structures of the [La(cb-tedpa)Cl], [Gd(cb-tedpa)](+), and [Lu(Me2tedpa)](+) complexes indicate octadentate binding of the ligands to the metal ions. The analysis of the Yb(3+)-induced shifts in [Yb(Me2tedpa)](+) indicates that this complex presents a solution structure very similar to that observed in the solid state for the Lu(3+) analogue. The X-ray structures of [La(H2Me2tedpa)2](3+) and [Yb(H2Me2tedpa)2](3+) complexes confirm the exocyclic coordination of the metal ions, which gives rise to coordination polymers with the metal coordination environment being fulfilled by oxygen atoms of the picolinate groups and water molecules. The X-ray structure of [Gd(Hcb-tedpa)2](+) also indicates exocyclic coordination that in this case results in a discrete structure with an eight-coordinated metal ion. The nonreinforced complexes [Ln(Me2tedpa)](+) were prepared and isolated as chloride salts in nonaqueous media. However, these complexes were found to undergo dissociation in aqueous solution, except in the case of the complexes with the smallest Ln(3+) ions (Ln(3+) = Yb(3+) and Lu(3+)). A DFT investigation shows that the increased stability of the [Ln(Me2tedpa)](+) complexes in solution across the lanthanide series is the result of an increased binding energy of the ligand due to the increased charge density of the Ln(3+) ion. more...
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- 2016
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14. Exploring the Syntheses of Novel Glycomimetics: Carbohydrate Derivatives with Se-S- or Se-Se- Glycosidic Linkages
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Tünde Zita Illyés, Katalin E. Kövér, István Timári, Sára Balla, Attila Bényei, Ambati Ashok Kumar, and László Szilágyi
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chemistry.chemical_classification ,Természettudományok ,010405 organic chemistry ,Chemistry ,Stereochemistry ,Glycosidic bond ,General Chemistry ,Carbohydrate ,010402 general chemistry ,Kémiai tudományok ,01 natural sciences ,0104 chemical sciences - Abstract
KA
- Published
- 2016
15. Bioactive rearranged limonoids from the Chinese mangroveXylocarpus granatum Koenig
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Orazio Taglialatela-Scafati, Attila Mándi, Wen Zhang, Jia Li, Zhen Fang Zhou, Yue-Wei Guo, Hai-Li Liu, Attila Bényei, Tibor Kurtán, Z., Zhou, H., Liu, W., Zhang, Ti, Kurtán, A., Mándi, A., Bényei, J., Li, TAGLIALATELA SCAFATI, Orazio, and Y., Guo more...
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Circular dichroism ,biology ,Chemistry ,Stereochemistry ,Organic Chemistry ,Limonoid ,biology.organism_classification ,Biochemistry ,Protein Tyrosine Phosphatase 1B ,Természettudományok ,Xylocarpus granatum ,Drug Discovery ,medicine ,Mangrove ,Kémiai tudományok ,medicine.drug - Abstract
Two new pyridine-containing limonoids, xylogranatopyridines A and B (1 and 2) and their formal precursor, prexylogranatopyridine (3) were isolated from the twigs and leaves of the Chinese mangrove, Xylocarpus granatum. Xylogranatopyridine B (2) possesses an unprecedented rearranged B-ring together with a seco-ring A, supporting the biogenetic connection of 1–2 with 3. The chemical structures were elucidated by means of detailed spectroscopic analysis and X-ray single-crystal diffraction. The absolute configurations were assigned using electronic solid-state circular dichroism (ECD) supported by time-dependent density functional theory (TDDFT) ECD calculations and X-ray analysis. Xylogranatopyridine A (1) exhibited a significant inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with an IC50 value of 22.9 μM. This is the first report of PTP1B inhibitory activity of limonoids. more...
- Published
- 2014
16. Lower denticity leading to higher stability: structural and solution studies of Ln(III)-OBETA complexes
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Giovanni B. Giovenzana, Zsolt Baranyai, Roberto Negri, Lorenzo Tei, Attila Bényei, Carlos Platas-Iglesias, Judit Bodnár, Adrienn Vágner, and Mauro Botta
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Models, Molecular ,Magnetic Resonance Spectroscopy ,Denticity ,Molecular Structure ,Ligand ,Inorganic chemistry ,Nuclear magnetic resonance spectroscopy ,Crystal structure ,Crystallography, X-Ray ,Ligands ,Dissociation (chemistry) ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Természettudományok ,Stability constants of complexes ,Organometallic Compounds ,Chemical stability ,Physical and Theoretical Chemistry ,Ethylamine ,Kémiai tudományok - Abstract
The heptadentate ligand OBETA (2,2'-oxybis(ethylamine)-N,N,N',N'-tetraacetic acid) was reported to form complexes with Ln(3+) ions more stable than those formed by the octadentate and more popular congener EGTA (ethylene glycol O,O'-bis(ethylamine)-N,N,N',N'-tetraacetic acid). The structural features leading to this puzzling coordination paradox were investigated by X-ray diffraction, solution state NMR, molecular modeling, and relaxometric studies. The stability constant of Gd(OBETA) (log KGdL = 19.37, 0.1 M KCl) is 2 orders of magnitude higher than that of the higher denticity analogue Gd(EGTA) (log KGdL = 17.66, 0.1 M KCl). The half-lives (t1/2) for the dissociation reactions of Gd(OBETA) and Gd(EGTA) ([Cu(2+)]tot = 0.2 mM, [Cit(3-)]tot = 0.5 mM, [PO4(3-)]tot = 1.0 mM, and [CO3(2-)]tot = 25 mM at pH = 7.4 and 25 °C in 0.1 M KCl solution) are 6.8 and 0.63 h, respectively, reflecting the much higher inertness of Gd(OBETA) near physiological conditions. NMR studies and DFT calculations using the B3LYP functional and a large-core ECP indicate that the [Gd(OBETA)(H2O)2](-) complex most likely exists in solution as the Δ(λλ)(δδδδ)A/Λ(δδ)(λλλλ)A enantiomeric pair, with an activation free energy for the enantiomerization process of ∼40 kJ·mol(-1). The metal ion is nine-coordinate by seven donor atoms of the ligand and two inner-sphere water molecules. The X-ray crystal structure of [C(NH2)3]3[Lu(OBETA)(CO3)]·2H2O is in agreement with the predictions of DFT calculations, the two coordinated water molecules being replaced by a bidentate carbonate anion. The (1)H NMRD and (17)O NMR study revealed that the two inner-sphere water molecules in Gd(OBETA) are endowed with a relatively fast water exchange rate (kex(298) = 13 × 10(6) s(-1)). The higher thermodynamic stability and inertness of Ln(OBETA) complexes, peaking in the center of the 4f series, combined with the presence of two coordinated water molecules suggests that Gd(OBETA) is a promising paramagnetic probe for MRI applications. more...
- Published
- 2014
17. Two in one: Charged tertiary phosphines held together by ionic or covalent interactions as bidentate phosphorus ligands for synthesis of half-sandwich Ru(II)-complexes
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Péter Juhász, Ágnes Kathó, Ferenc Joó, Antal Udvardy, and Attila Bényei
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Denticity ,Stereochemistry ,Phosphorus ,Ionic bonding ,chemistry.chemical_element ,Ion pairs ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Természettudományok ,Covalent bond ,Polymer chemistry ,Materials Chemistry ,Physical and Theoretical Chemistry ,Triphenylphosphine ,Benzene ,Kémiai tudományok - Abstract
Ion pairs consisting of N-substituted derivatives of 1,3,5-triaza-7-phosphaadamantane (pta-R; R = benzyl, butyl, hexyl) as cations and monosulfonated triphenylphosphine (mtppms) as anion were synthesized and characterized (including X-ray diffraction, too). These ion pairs act as bidentate phosphorus ligands in reactions with [(η6-C10H14)RuCl2]2, yielding mononuclear or dinuclear half sandwich Ru(II) complexes. Bisphosphine 3 of good water-solubility was synthesized in reaction of pta with 1,4-bis(chloromethyl)benzene and used for the synthesis of the water-soluble dinuclear complex [{(η6-C10H14)RuCl2}2(μ-3)]Cl2. more...
- Published
- 2013
18. Vanadate complexes in serum: a speciation modeling study
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Tamás Kiss, Attila Bényei, Annalisa Dean, Valerio Di Marco, Tamás Jakusch, and Tamas Oncsik
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O ligands ,vanadium ,solution chemistry ,NMR ,X-ray diffraction ,transferrin ,Inorganic chemistry ,Maltol ,Vanadium ,chemistry.chemical_element ,Crystal structure ,Picolinic acid ,Fluorescence spectroscopy ,Inorganic Chemistry ,Metal ,chemistry.chemical_compound ,Természettudományok ,medicine ,Vanadate ,Kémiai tudományok ,Human serum albumin ,chemistry ,visual_art ,visual_art.visual_art_medium ,medicine.drug - Abstract
The speciations of two drug candidate ligands, 2-hydroxypyridine-N-oxide (Hhpno) and 2-mercaptopyridine-N-oxide (Hmpno), with vanadate (V(V)) were determined at 25.0 degrees C and 0.20 mol dm(-3) KCl by pH-metric and (51)V-NMR methods. At pH 7.4, the two predominant compounds with both ligands are the VO(2)L(2) and VO(2)L(OH). NH(4)[VO(2)(hpno)(2)] x 3 H(2)O was prepared in solid form, and its crystal structure was determined by X-ray diffraction. The stabilities of the complexes VO(2)L(2) of five drug candidate ligands were compared at pH 7.4. In view of the stability sequence hpnomaltol approximately hdp (Hhdp: 3-hydroxy-1,2-dimethyl-4-pyridinone)mpnopicolinic acid, the first two of these ligands were chosen for equilibrium studies with apotransferrin (apoTf) competition. The V(V)-apoTf stability constants (log K(1) = 6.03 +/- 0.10; log K(2) = 5.46 +/- 0.18) determined by (51)V-NMR spectroscopy were confirmed by ultrafiltration. Both methods proved that there seems to be no hydrogencarbonate-vanadate competition for the apoTf anion-binding positions. The other potential high molecular mass V(V) binder in the serum is human serum albumin (HSA). As no interaction was detected by (51)V-NMR spectroscopy or fluorimetry, the binding properties of HSA were quantified on the basis of literature data. As a final conclusion, speciation modeling calculations suggest that, under serum conditions, apoTf is probably the primary metal ion binder, even in the presence of the most stable V(V) carrier ligands hpno and maltol and HSA plays a negligible role in V(V) binding. more...
- Published
- 2010
19. tert-Amino Effect in peri-Substituted Naphthalenes: Syntheses of Naphthazepine and Naphthazonine Ring Systems
- Author
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Péter Mátyus, Krisztina Ludányi, Attila Bényei, and Ágota Anna Földi
- Subjects
chemistry.chemical_classification ,Hydride ,Stereochemistry ,Organic Chemistry ,Ring (chemistry) ,Aldehyde ,chemistry.chemical_compound ,Suzuki reaction ,chemistry ,Természettudományok ,Intramolecular force ,Methylene ,Azepine ,Kémiai tudományok - Abstract
Novel straightforward syntheses of naphtho-fused azepines and benzazonine via tert-amino effect are described. Starting from 1-naphthylamine, 8-/N,N-dialkylaminonaphthalene-1-carbaldehydes could be obtained in two steps. The aldehyde was prepared by a Suzuki reaction of 8-bromonaphthalene-1-carbaldehyde with ortho-pyrrolidinophenylboronic acid. Treatment of aldehydes with active methylene compounds afforded naphthazepines and novel benzazonine ring system, respectively, through rearrangement of isolable vinyl intermediates or benzo[de]quinolinium derivatives or without isolation of any intermediates. A mechanistic investigation supports an intramolecular hydride transfer for the ring closure to azepine or azonine. Our results indicate that the tert-amino effect may provide a valuable approach to the synthesis of ortho- and peri-fused aza-ring systems. more...
- Published
- 2010
20. Equilibrium and kinetic properties of the lanthanoids(III) and varioous divalent metal complexes of the heptadentate ligand AAZTA
- Author
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Silvio Aime, Attila Bényei, Ernő Brücher, Fulvio Uggeri, Giovanni B. Giovenzana, and Zsolt Baranyai
- Subjects
Lanthanide ,Denticity ,Ligand ,Chemistry ,Metal ions in aqueous solution ,Organic Chemistry ,Kinetics ,Inorganic chemistry ,Contrast Media ,General Chemistry ,Ligands ,Lanthanoid Series Elements ,Magnetic Resonance Imaging ,Catalysis ,Dissociation (chemistry) ,Ion ,Crystallography ,Transmetalation ,Természettudományok ,Metals ,Thermodynamics ,Protons ,Kémiai tudományok - Abstract
The heptadentate ligand 1,4-bis(hydroxycarbonylmethyl)-6-[bis(hydroxycarbonylmethyl)]amino-6-methylperhydro-1,4-diazepine (AAZTA) and its derivatives were recently reported to give stable complexes with Gd(3+) with superior efficiency as MRI contrast agents. Nevertheless, only preliminary data are available on the coordination behavior of this interesting ligand. In this work, thermodynamic and kinetic stability data are determined for the formation of complexes with AAZTA and the lanthanoid metal ions, and other divalent metal ions of interest for this application. The AAZTA ligand binds the lanthanoid ions with log K(ML) values of 17.53-21.85 with its affinity steadily increasing from La(3+) to Lu(3+), suggesting that the seven-membered skeleton is better suited to accommodate smaller metal ions. Even though the denticity is lower, the stability of the heavier lanthanoid complexes is comparable to those of the classical ligand diethylenetriaminepentaacetic acid (DTPA). The transmetalation reactions of [Gd(AAZTA)](-) with Cu(2+) and Eu(3+) predominantly occur through proton-assisted dissociation of the complex. The role of the direct attack of Cu(2+) or Eu(3+) in the exchange reactions is limited, although the formation of dinuclear complexes decreases the proton-assisted dissociation. Near physiological conditions, [Gd(AAZTA)](-) is significantly more inert than [Gd(DTPA)](2-), allowing its potentially safe use as contrast agent in magnetic resonance imaging. more...
- Published
- 2009
21. Synthesis of a pericosine analogue with a bicyclo[2.2.2]octene skeleton
- Author
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Lieve Naesens, Attila Bényei, István Komáromi, Zsolt Fejes, Ferenc Fenyvesi, László Szilágyi, Pál Herczegh, and Attila Mándi
- Subjects
chemistry.chemical_compound ,chemistry ,Bicyclic molecule ,Természettudományok ,Stereochemistry ,Organic Chemistry ,Drug Discovery ,Regioselectivity ,Methyl gallate ,Octene ,Kémiai tudományok ,Biochemistry ,Chemical synthesis - Abstract
A new analogue of the antitumor pericosines possessing a bicyclo[2.2.2]octene skeleton has been synthesized from methyl gallate using oxidative dearomatization and regio- and diastereoselective Diels–Alder reaction as the key steps. more...
- Published
- 2009
22. Substituent dependent fluorescence response of diazacrown-based PET sensors
- Author
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Péter Kele, Zoltán Szakács, András Kotschy, Krisztina Nagy, Szabolcs Béni, Attila Bényei, and Béla Noszál
- Subjects
Steric effects ,Fluorophore ,Organic Chemistry ,Analytical chemistry ,Substituent ,Photochemistry ,Biochemistry ,Fluorescence ,chemistry.chemical_compound ,chemistry ,Természettudományok ,Drug Discovery ,Proton NMR ,Ammonium ,Spectroscopy ,Kémiai tudományok ,Fluorescence response - Abstract
The sensing ability of three 1,10-diaza-18-crown-6 based sensors bearing a coumarin fluorophore was studied and compared with the analogous monoaza-18-crown-6 sensor. Coordination experiments between hosts and organic ammonium salts with varying steric demand were studied using fluorescence and 1 H NMR spectroscopy. We have found that the fluorescent signal generated on complexation was greatly influenced by the structure of the sensor. Surprisingly, in two cases, we observed the decrease of fluorescence on complexation, which was attributed to changes in the conformational dynamics of the sensors on complexation. more...
- Published
- 2008
23. Complexation Properties of the Di-, Tri-, and Tetraacetate Derivatives of Bis(aminomethyl)phosphinic Acid.
- Author
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Gyula Tircsó, Attila Bényei, Róbert Király, István Lázár, Róbert Pál, and Ernő Brücher
- Published
- 2007
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